218 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



usually terminate in three much elongated, pointed, and rather stout 

 spinules (pi. 98, fig. 16). The small club spines of the dorsal surface 

 of the upper arm plates are short, rather broad, and carry two or 

 three rather well developed and subequal spinules (fig. l<z) . 



In both specimens the first ventral spine rapidly becomes con- 

 verted into a hook resembling that which I have described in O. 

 aspidota; that is to say, it shows on its concave border seven or eight 

 parallel points, while its convex border bears toward the tip two or 

 three asperities (pi. 98, fig. Ic). The tentacle scale is large and 

 elongated, terminated sometimes by a single elongated point, some- 

 times by two or three unequal points (e). 



OPHIOTHRIX CRASSISPINA Koehler. 



Plate 49, figs. 1-6 ; plate 50, fig. 1 ; plate 52, figs. 3-5 ; plate 98, fig. 2. 



Ophiothrix crassispina KCEHLEB ('04), p. 147, pi. 28, figs. 3-5; pi. 29, fig. 1; 

 pi.. 30, fig. 4. H. L. CLARK ('15), p. 280. 



Localities. Albatross station 5168; Sulu (Jolo) Archipelago, 

 Tawi Tawi Group ; Observation Island bearing N. 17 W., 7.78 kilo- 

 meters (4.2 miles) distant (lat. 4 56' 30" N., long. 119 45' 40" E.) ; 

 146 meters (80 fathoms) ; February 25, 1908; co. S. 



Four specimens (Cat. No. E. 144, U.S.N.M.). 



Albatross station 5170; Sulu Archipelago, Tawi Tawi Group; 

 Sibutu Island (south end) bearing N. 38 E., 25.02 kilometers (13.5 

 miles) distant (lat. 4 28' 00" N., long. 119 19' 30" E.) ; 234 meters 

 (128 fathoms) ; February 27, 1908; crs. S. 



One specimen (Cat. No. E. 145, U.S.N.M.). 



Notes. The specimens are of different sizes; in the largest the 

 diameter of the disk is 7.5 mm., and the arms are between 30 mm. 

 and 35 mm. in length ; in the others the diameter of the disk varies 

 between 6 mm. and 4 mm. 



They agree well with the type which I described from two speci- 

 mens collected by the Siboga in the Sunda Archipelago, in which 

 the diameter of the disk varies between 7 mm. and 9 mm. 



The photographs which I reproduce here (pi. 49, figs. 1-6; pi. 50, 

 fig. 1; pi. 52, figs. 3-5) render it unnecessary for me to describe the 

 modifications of the arm spines ; it is sufficient to complete in certain 

 respects my description of 1904. 



I described the arm spines as eight in number, adding that the 

 length increased from the first to the sixth ; this progressive elonga- 

 tion may be especially well appreciated on the photograph represent- 

 ing a fragment of an arm seen from the ventral surface (pi. 52, fig. 

 5), and it will be remarked that the three first spines remain very 

 short. I emphasize this character, as well as the number of the arm 

 spines, which will permit us to separate 0. crassispina from the new 



